In those movies where Santa IS real but no parents believe it where do they think the extra presents come from?

Wouldn't they be surprised at all to find a bunch of presents they didn't pay for? I mean if I woke up on Christmas, opened all my presents then went to thank my parents as I do every year only to have them tell me they didn't buy me all this and they have no idea where it came from, and then my Mom calls the police hysterically while my Dad checks on my little sister I'd freak the **** out!